“The image-bookmarking site and social network drew 18.7 million unique visitors in the U.S. in March, compared with 17.8 million in February and 11.7 million in January, says ComScore.

“AppData, meanwhile, says the number of Pinterest users connected to Facebook in the past 30 days declined to 8.3 million from 12.2 million.”

Of course, the numbers remain high, and Pinterest is still among the most popular social networks in the U.S. based on traffic. The Wall blog recently offered some interesting facts and stats about Pinterest:

1. Pinterest is driving as much referral traffic as Twitter and Google and in fact has surpassed YouTube, Reddit, Reddit and Google Plus in referral traffic (Shareaholic, Feb. 2012)
2. Pinterest emerged as the third-most popular social network in the U.S. after Facebook and Twitter (a very recent Experian “2012 Digital Marketer: Benchmark and Trend” report)
3. This month, two of the biggest online players, Amazon and eBay, added Pinterest buttons to their product pages (enabling Pinners to share product images, including links to product pages, on their virtual pin-boards direct from retailers’ websites).

Also, according to the Pinterest blog, Monday and Tuesday were the site’s highest traffic days thus far.

USA Today quoted several analysts who explained the plateau. One indicated it’s a “natural hiccup” in the site’s meteoric rise.